Film forming method, film forming device, and method for manufacturing semiconductor device

ABSTRACT

A film forming method includes: providing the substrate into the processing container; forming a metal-based film on the substrate within the processing container; and subsequently, supplying a Si-containing gas into the processing container in a state in which the substrate is provided within the processing container.

TECHNICAL FIELD

The present disclosure relates to a film forming method, a film formingapparatus, and a semiconductor device manufacturing method.

BACKGROUND

In a semiconductor device manufacturing process, for example, ametal-based film such as a TiN film is used for various uses such as anelectrode, such as a lower electrode of a DRAM, or a barrier film. Ageneral thin film forming technique is used for forming a metal-basedfilm such as a TiN film, and Patent Document 1 describes forming a TiNfilm by an atomic layer deposition method (ALD method).

PRIOR ART DOCUMENTS Patent Document

Patent Document 1: Japanese laid-open publication No. 2015-78418

SUMMARY

The present disclosure provides a film forming method, a film formingapparatus, and a semiconductor device manufacturing method capable ofsuppressing oxidation of a film surface when forming a metal-based film.

A film forming method according to an aspect of the present disclosureincludes: providing a substrate into the processing container; forming ametal-based film on the substrate within the processing container; andthen supplying a Si-containing gas into the processing container in astate in which the substrate is provided within the processingcontainer.

According to the present disclosure, a film forming method, a filmforming apparatus, and a semiconductor device manufacturing methodcapable of suppressing oxidation of a film surface when forming ametal-based film are provided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 a flowchart illustrating a film forming method according to anembodiment.

FIGS. 2A to 2C are cross-sectional views illustrating steps of the filmforming method according to the embodiment.

FIG. 3 is a cross-sectional view illustrating an example of a filmforming apparatus when a film forming method of an embodiment is appliedto the formation of a TiN film.

FIG. 4 is a cross-sectional view illustrating a structural example of asemiconductor wafer on which a film forming process is performed by theapparatus of FIG. 3 .

FIG. 5 is a cross-sectional view illustrating a state in which a TiNfilm is formed on the semiconductor wafer of FIG. 4 .

FIG. 6 is a cross-sectional view illustrating a state in which a surfacelayer is formed on a surface of a TiN film by performing a step ofsupplying DCS gas, which is a Si-containing gas, into the chamber afterthe formation of the TiN film.

FIG. 7 is a timing chart illustrating a specific gas supply sequence ofa TiN film forming step and a Si-containing gas supply step in a case inwhich SiH₄ gas is supplied once (1 cycle) as a Si-containing gas.

FIG. 8 is a timing chart illustrating a specific gas supply sequence ofa TiN film forming step and a Si-containing gas supply step in a case inwhich SiH₄ gas is supplied multiple times (multiple cycles) as aSi-containing gas.

FIG. 9 is a specific gas supply sequence of a TiN film forming step anda Si-containing gas supply step in a case in which SiH₄ gas and NH₃ gasare alternately supplied multiple times.

FIG. 10 is a diagram showing the relationship between a flow rate of DCSgas and a specific resistance of a TiN film.

FIG. 11 is a diagram showing the relationship between a supply time ofDCS gas and a specific resistance of a TiN film.

FIG. 12 is diagram showing the results of measuring sheet resistances ofTiN films and the uniformities thereof in a case in which supply of SiH₄gas as a Si-containing gas supply step is performed for one cycle, acase in which supply of SiH₄ gas is performed for five cycles withpurging interposed between cycles, and a case in which supply of SiH₄gas is not performed after forming a TiN film.

FIG. 13 is diagram showing the results of measuring sheet resistances ofTiN films and the uniformities thereof in a case in which supply of SiH₄gas as a Si-containing gas supply step and supply of NH₃ gas areperformed for one cycle, a case in which supply of SiH₄ gas and supplyof NH₃ gas are performed for five cycles, and a case in which supply ofSiH₄ gas is not performed after forming a TiN film.

FIG. 14 is a cross-sectional view illustrating a state in which a SiGefilm is formed after a surface layer is formed on the surface of a TiNfilm.

DETAILED DESCRIPTION

Hereinafter, embodiments will be described with reference to theaccompanying drawings.

<Embodiment of Film Forming Method>

First, an embodiment of a film forming method will be described.

FIG. 1 is a flowchart illustrating a film forming method according to anembodiment and FIGS. 2A to 2C are sectional views of steps of the filmforming method. As illustrated in FIG. 1 and FIGS. 2A to 2C, a filmforming method according to the present embodiment includes: a step ofproviding a substrate 201 into a processing container of a film formingapparatus (step 1 in FIG. 2A); a step of forming a metal-based film 202on the substrate 201 within the processing container (step 2 in FIG.2B); and then a step of supplying a Si-containing gas into theprocessing container in a state in which the substrate 201 is providedinto the processing container (step 3 in FIG. 2C).

In step 1, the substrate 201 on which a metal-based film is to be formedis disposed within the processing container of the film formingapparatus to prepare for film formation. The substrate 201 is notparticularly limited, but a semiconductor substrate (a semiconductorwafer) including a semiconductor base body, such as silicon, isexemplified. The substrate 201 in this case may be the semiconductorbase body itself, or may be a substrate in which one or more filmshaving a desired function are formed on a semiconductor base body.

Examples of the metal-based film 202 formed on the substrate 201 in step2 include a metal film and a metal compound film the characteristics ofwhich may be deteriorated due to oxidation. Specific examples include aTi film, a TiN film, a Ta film, a TaN film, a W film, an Al film, a Mofilm, a Ru film, a Co film, and a Ni film.

The method of forming the metal-based film 202 is not particularlylimited, and thin film forming techniques such as an ALD method, a CVDmethod, and a PVD method are exemplified. From the viewpoint ofobtaining a good step coverage, the ALD method is desirable.

Step 3 is a post-film forming process in which a Si-containing gas issupplied into the processing container after the metal-based film 202 isformed. By supplying the Si-containing gas, the Si-containing gas isadsorbed on the surface of the metal-based film, and a surface layer 203containing Si is formed.

Ammonia (NH₃), which is a reaction gas that reacts with another gas, forexample, the Si-containing gas, or an inert gas may be supplied togetherwith the Si-containing gas. The Si-containing gas is not particularlylimited, but examples thereof include a silane-based compound, achlorosilane-based compound, and an organic silane-based compound.Examples of the silane-based compound include silane (monosilane) anddisilane. Examples of the chlorosilane-based compound includedichlorosilane, monochlorosilane, trichlorosilane, silicontetrachloride,and hexachlorodisilane. Examples of the organic silane-based compoundinclude aminosilane-based compounds such as butylaminosilane, bistertiary butylaminosilane, and dimethylaminosilane. Among these, atleast one of dichlorosilane, silane, and disilane, which are generallyused in a semiconductor manufacturing process, may be preferably used.

When only a Si-containing gas or a Si-containing gas and an inert gasare supplied, the Si-containing gas may be thermally decomposed to forma Si layer as the surface layer 203. The surface layer 203 may have areaction layer in which Si and a base have reacted with each other. Whenthe reaction gas is supplied in addition to the Si-containing gas, a Sicompound layer may be formed as the surface layer 203 by the reactionbetween the Si-containing gas and the reaction gas. For example, when anitrogen-containing gas such as NH₃ gas is used as the reaction gas, aSiN layer may be formed as the surface layer 203.

The temperature and pressure conditions in the step of supplying theSi-containing gas in step 3 differ slightly depending on theSi-containing gas to be used, but the temperature is preferably in therange of 400 to 700 degrees C., and the pressure is preferably in therange of 266.6 to 13,332.2 Pa (2 to 100 Torr).

The supply of Si-containing gas may be performed once or repeatedmultiple times. When the supply of the Si-containing gas is performedonce, it is possible to control the adsorption amount by the supplytime. In this case, the supply time of the Si-containing gas ispreferably 0.05 to 20 sec. In addition, by repeating the supply of theSi-containing gas multiple times, it is possible to control theadsorption amount of the Si-containing gas by the number of times, andto improve the controllability of the layer thickness of the surfacelayer 203. In this case, the supply time of the Si-containing gas at onetime is preferably 0.05 to 4 sec, and the number of times (the number ofcycles) of supplying the Si-containing gas is preferably in the range of1 to 5 times. In addition, it is preferable to perform purging with aninert gas between the cycles of supplying the Si-containing gas.

When a reaction gas is supplied in addition to the Si-containing gas,the reaction gas may be supplied after the Si-containing gas issupplied, or the Si-containing gas and the reaction gas may bealternately supplied multiple times. By alternately supplying theSi-containing gas and the reaction gas multiple times, it is possible toform a Si compound layer as the surface layer 203 with good layerthickness controllability. The Si-containing gas and the reaction gasmay be supplied at the same time. By using, for example, NH₃ gas as thereaction gas, it is possible to form a SiN layer as the surface layer203.

When the surface layer 203 is formed by supplying the Si-containing gas,the adsorption amount of the Si-containing gas is not particularlylimited, and the effect of suppressing oxidation is obtained with one ormore molecular layers. When the adsorption amount of the Si-containinggas becomes too large, there is concern about the influence on thecharacteristics. Therefore, the adsorption amount is preferably 15 nm orless in terms of film thickness, and the thickness of the surface layer203 is preferably in the range of 0.5 to 1 nm. Similarly, when theSi-containing gas and the reaction gas are supplied to form a Sicompound layer such as a SiN layer as the surface layer 203, thethickness of the surface layer 203 is preferably in the range of 0.5 to1 nm.

The reason for performing the step of supplying the Si-containing gasafter forming the metal-based film in this way will be described below.

After the metal-based film is formed, the substrate is carried out fromthe processing container and provided for the next step. When thesubstrate is carried out into the atmosphere before the next step, theformed metal-based film is oxidized from the surface in a bulk directionby being exposed to oxygen or moisture in the atmosphere, and thus acharacteristic thereof is deteriorated. For example, the resistance ofthe film increases. In particular, when the film thickness is thin, theinfluence of oxidation from the surface becomes large, and thus thecharacteristic deterioration becomes remarkable.

Therefore, after forming the metal-based film 202 on the substrate 201within the processing container, the surface layer 203 is formed bysupplying the Si-containing gas into the processing container such thatthe Si-containing gas is adsorbed on the surface of the metal-based film202. As a result, since the substrate is carried out in a state in whichthe surface of the metal-based film 202 is not exposed, oxidation of themetal-based film 202 is suppressed.

The next step may be performed in another processing container of thevacuum system. However, even in that case, since the metal-based film isslightly oxidized by oxygen or moisture in a vacuum transport system,the effect of suppressing oxidation by the step of supplying theSi-containing gas is exhibited.

Since the surface layer 203 is formed when the Si-containing gasadsorbed on the surface of the metal-based film 202 is heated, thesurface layer 203 may have a reaction layer due to the reaction betweenthe adsorbed Si-containing gas and the surface of the metal-based film.

As described above, as the film thickness is thinner, the effect ofoxidation of the metal-based film is greater, and characteristicdeterioration, such as increased resistance, appears remarkably.Therefore, when the film thickness of the metal-based film is 5 nm orless, the effect of suppressing oxidation by the Si-containing gas isgreater.

After the step of supplying the Si-containing gas, the substrate iscarried out from the processing container, and the next film formingstep is performed by another film forming apparatus. At this time, sincethe surface layer containing Si is formed on the surface of themetal-based film on the substrate, if the next film forming step is astep of forming a Si-containing film, the affinity is improved. At thistime, since Si is present on the surface on which the Si-containing filmis formed, a good effect such as shortening the incubation time whenforming the Si-containing film can be obtained.

<Application to Formation of TiN Film>

Next, formation of a TiN film will be described as a specificapplication example.

A TiN film as a metal-based film is used as a barrier film or anelectrode, and is required to have a low electrical resistance. For theformation of a TiN film, an ALD method, which is capable of obtaining afilm of good film quality with a high step coverage, is often used.After the TiN film is formed, the next step of a film forming process,for example, a formation of a SiGe film, is performed. In that case,since both film formations are performed in different apparatuses, afterthe TiN film is formed, the substrate is carried out into theatmosphere. At this time, there arises a problem in that it is difficultto obtain good device characteristics because the TiN film is oxidizedby moisture or oxygen in the atmosphere and the thus resistance isincreased. Therefore, a step of supplying a Si-containing gas isperformed to form a surface layer on the surface of the TiN film so asto suppress the oxidation of the TiN film after the substrate is carriedout from the processing container.

The details will be described below.

[Film Forming Apparatus for TiN Film]

FIG. 3 is a cross-sectional view illustrating an example of a filmforming apparatus when a film forming method of an embodiment is appliedto the formation of a TiN film.

The film forming apparatus 100 includes a chamber 1 as a processingcontainer, a susceptor (a substrate placement stage) 2, a shower head 3,an exhaust part 4, a gas supply mechanism 5, and a controller 6.

The chamber 1 is made of a metal such as aluminum, and has asubstantially cylindrical shape. A carry-in/out port 26 through which asemiconductor wafer (hereinafter, simply referred to as a wafer) W,which is a substrate, is carried in/out with respect to a vacuumtransport chamber (not illustrated) by a transport mechanism (notillustrated), is formed in the side wall of the chamber 1, and thecarry-in/out port 26 is configured to be openable/closable by a gatevalve 27. An annular exhaust duct 28 having a rectangular cross sectionis provided on the main body of the chamber 1. A slit 28 a is formedalong the inner peripheral surface of the exhaust duct 28. In addition,an exhaust port 28 b is formed in the outer wall of the exhaust duct 28.On the top surface of the exhaust duct 28, a ceiling wall 29 is providedto close the upper opening of the chamber 1. The space between theceiling wall 29 and the exhaust duct 28 is hermetically sealed with aseal ring 30.

The susceptor 2 is configured to place thereon a wafer W, which is asubstrate, within the chamber 1, has a disk shape having a sizecorresponding to the wafer W, and is provided horizontally. Thesusceptor 2 is supported on a support member 33. A heater 31 for heatingthe wafer W is embedded in the susceptor 2. The heater 31 is suppliedwith power from a heater power supply (not illustrated) to generateheat. Then, by controlling the output of the heater 31, the wafer W iscontrolled to a predetermined temperature. The susceptor 2 is providedwith a ceramic cover member 32 to cover the outer peripheral region ofthe wafer placement surface and the side surface of the susceptor.

The support member 33, which supports the susceptor 2, extends from thecenter of the bottom surface of the susceptor 2 through a hole formed inthe bottom wall of the chamber 1 to the lower side of the chamber 1, andthe lower end of the support member 33 is connected to a liftingmechanism 34. The susceptor 2 is configured to be raised and loweredbetween a processing position illustrated in FIG. 3 and a transportposition at which wafer can be transported by the lifting mechanism 34via the support member 33. The transport position is indicated by analternating long and two short dashes line. In addition, a flange 35 isprovided on the support member 33 below the chamber 1, and a bellows 36,which partitions the atmosphere within the chamber 1 from the ambientair, is provided between the bottom surface of the chamber 1 and theflange 35 to expand and contract in response to the raised and loweredoperation of the susceptor 2.

Three wafer support pins 37 (of which only two are illustrated) areprovided in the vicinity of the bottom surface of the chamber 1 toprotrude upward from a lifting plate 37 a. The wafer support pins 37 areconfigured to be raised and lowered via the lifting plate 37 a by thelifting mechanism 38 provided below the chamber 1, and are insertedthrough through-holes 22 provided in the susceptor 2 located at thetransport position to be movable upward or downward with respect to thetop surface of the susceptor 2. This causes delivery of a wafer W to beperformed between the wafer transport mechanism (not illustrated) andthe susceptor 2.

The shower head 3 is configured to supply a processing gas into thechamber 1 in the form of a shower, and is provided in the upper portionof the chamber 1 to face the susceptor 2 and has substantially the samediameter as the susceptor 2. The shower head 3 includes a main body 39fixed to the ceiling wall 29 of the chamber 1 and a shower plate 40connected to the lower side of the main body 39. A gas diffusion space41 is formed between the main body 39 and the shower plate 40.

In the gas diffusion space 41, a plurality of gas diffusion members 42are provided. A plurality of gas discharge holes are formed around thegas diffusion members 42. The gas diffusion members 42 are connected,respectively, to one ends of a plurality of gas supply paths 43, whichare provided in the main body 39. The other ends of the gas supply paths43 are connected to a diffusion part 44 formed in the central portion ofthe top surface of the main body 39. In the central portion of the mainbody 39, three gas introduction holes 45 a, 45 b, and 45 c penetratingthe main body 39 from the top surface thereof to the diffusion part 44are provided.

An annular protrusion 40 b protruding downward is formed at theperipheral edge of the shower plate 40, and gas ejection holes 40 a areformed in the flat surface inside the annular protrusion 40 b of theshower plate 40. In the state in which the susceptor 2 is located at theprocessing position, a processing space S is formed between the showerplate 40 and the susceptor 22, and the annular protrusion 40 b and thetop surface of the cover member 32 of the susceptor 2 are located closeto each other to form an annular gap 48 therebetween.

The exhaust part 4 includes: an exhaust pipe 46 connected to the exhaustport 28 b in the exhaust duct 28; and an exhaust mechanism 47 connectedto the exhaust pipe 46 and including a vacuum pump, a pressure controlvalve, or the like. During processing, the gas within the chamber 1reaches the exhaust duct 28 via the slit 28 a, and is exhausted from theexhaust duct 28 through the exhaust pipe 46 by the exhaust mechanism 47of the exhaust part 4.

The processing gas supply mechanism 5 includes a TiCl₄ gas source 51, anNH₃ gas source 52, a dichlorosilane (DCS) gas source 53, a first N₂ gassource 54, a second N₂ gas source 55, and a third N₂ gas source 56. TheTiCl₄ gas source 51 supplies TiCl₄ gas, which is a Ti raw material gas.The NH₃ gas source 52 supplies NH₃ gas, which is a nitride gas (reducinggas). The DCS gas source 53 supplies DCS gas, which is a Si-containinggas. The first to third N₂ gas sources 54, 55, and 56 supply N₂ gas as acarrier gas and a purge gas. The carrier gas and the purge gas are notlimited to the N₂ gas, and other inert gases such as Ar gas may be used.

One end of a TiCl₄ gas supply pipe 61 is connected to the TiCl₄ gassource 51. One end of an NH₃ gas supply pipe 62 is connected to the NH₃gas source 52. One end of a DCS supply pipe 63 is connected to the DCSgas source 53. One end of a first N₂ gas supply pipe 64, a second N₂ gassupply pipe 65, and a third N₂ gas supply pipe 66 are connected to thefirst N₂ gas source 54, the second N₂ gas source 55, and the third N₂gas source 56, respectively. The other end of the TiCl₄ gas supply pipe61 is connected to the gas introduction hole 45 a, the other end of theNH₃ gas supply pipe 62 is connected to the gas introduction hole 45 b,and the other end of the DCS gas supply pipe 63 is connected to the gasintroduction hole 45 c. The other end of the first N₂ gas supply pipe 64is connected to the TiCl₄ gas supply pipe 61, the other end of thesecond N₂ gas supply pipe 65 is connected to the NH₃ gas supply pipe 62,and the other end of the third N₂ gas supply pipe 66 is connected to theDCS gas supply pipe 63. A branch pipe 62 a is branched in the middle ofthe NH₃ gas supply pipe 62, and the other end of the branch pipe 62 ajoins the NH₃ gas supply pipe 62. By providing the branch pipe 62 a inthis way, it is possible to supply a large flow rate of NH₃ gas. TheTiCl₄ gas supply pipe 61, the NH₃ gas supply pipe 62, the branch pipe 62a, and the DCS gas supply pipe 63 are provided with opening/closingvalves 71, 72, 72 a, and 73 at the upstream sides of the joiningportions of the N₂ gas supply pipes, respectively. In addition, thefirst N₂ gas supply pipe 64, the second N₂ gas supply pipe 65, and thethird N₂ gas pipe 66 are provided with opening/closing valves 74, 75,and 76, respectively. In addition, the TiCl₄ gas supply pipe 61, the NH₃gas supply pipe 62, the DCS gas supply pipe 63, the first N₂ gas supplypipe 64, the second N₂ gas supply pipe 65, and third N₂ gas pipe 66 areprovided with flow rate controllers 81 to 86 at the upstream sides ofthe opening/closing valves thereof, respectively. As the flow ratecontrollers, for example, mass flow controllers may be used.

When a TiN film is formed, ALD film formation may be performed byconstantly opening the opening/closing valves 74, 75, and 76 of thefirst N₂ gas supply pipe 64, the second N₂ gas supply pipe 65, and thethird N₂ gas supply pipe 66 to constantly supply N₂ gas and operatingthe opening/closing valves 71, 72, and 72 a at a high speed in the statein which the opening/closing valve 73 is closed. When supplying a DCSgas, which is a Si-containing gas, the valves 71, 72, 72 a are closedand the opening/closing valve 73 is opened after the film formation.

A pipe that branches from each of the first N₂ gas supply pipe 64, thesecond N₂ gas supply pipe 65, and the third N₂ gas supply pipe 66 toincrease the flow rate of the N₂ gas only during purging may be providedto increase the flow rate of the N₂ gas during the purging step. Inaddition, the purge gas is not limited to N₂ gas, and may be anotherinert gas such as Ar gas.

As the Ti raw material gas, tetra(isopropoxy)titanium (TTIP), titaniumtetrabromide (TiBr₄), titanium tetraiodide (TiI₄),tetrakis(ethylmethylamino)titanium (TEMAT), andtetrakis(dimethylamino)titanium (TDMAT), tetrakis(diethylamino)titanium(TDEAT), or the like may also be used, in addition to the TiCl₄. As thenitriding gas (reducing gas), a hydrazine-based gas, such asmonomethylhydrazine (MMH), or the like may be used, in addition to theNH₃ gas. In addition, as the silicon-containing gas, various gases asdescribed above may be used, in addition to the DCS gas.

The controller 6 is configured with a computer, and includes a maincontroller including a CPU, an input device (e.g., a keyboard, a mouseor the like), an output device (e.g., a printer or the like), a displaydevice (e.g., a display or the like), and a storage device (a storagemedium). The main controller controls the operations of respectivecomponents, such as opening/closing of the opening/closing valves 71 to76, adjustment of gas flow rates via the flow rate controllers 81 to 86,adjustment of the pressure within the chamber 1 by a pressure controlvalve, and adjustment of the temperature of a wafer W by the heater 31.The control of these operations is executed by a processing recipe whichis a control program stored in a storage medium (e.g., a hard disk, anoptical disk, or a semiconductor memory) embedded in the storage device.

[Method of Forming TiN Film with Film Forming Apparatus of FIG. 3 ]

Next, a method for forming a TiN film in the film forming apparatus 100configured as described above will be described.

First, the gate valve 27 is opened, and a wafer W is carried into thechamber 1 from the vacuum transport chamber by the transport apparatusand placed on the susceptor 2. As the wafer W, for example, asillustrated in FIG. 4 , a wafer W having a patterned SiO₂ film 302 on aSi base body 301 is used.

After retracting the transport apparatus, the gate valve 27 is closedand the susceptor 2 is raised to the processing position. Next, N₂ gasis continuously supplied into the processing space S from the first N₂gas source 54, the second N₂ gas source 55, and the third N₂ gas source56 to maintain the interior of the chamber 1 at a predetermineddepressurized state, and the temperature of the susceptor 2 iscontrolled to a predetermined temperature by the heater 31.

Then, while maintaining the state in which the N₂ gas is continuouslysupplied, the opening/closing valves 71, 72, and 72 a are operated tosequentially supply TiCl₄ gas, which is a raw material gas, and NH₃ gas,which is a nitride gas (reducing gas), so that a TiN film, which is ametal-based film, is formed on the wafer W through an ALD method. Forexample, as illustrated in FIG. 5 , a TiN film 303 is formed on thepatterned SiO₂ film 302 of the wafer W.

At this time, the temperature of the susceptor 2 is preferably set to200 to 600 degrees C., and the pressure within the chamber 1 ispreferably set to 266.6 to 13,332.2 Pa (2 to 100 Torr).

After film formation, the opening/closing valves 71, 72, and 72 a areclosed, the supply of TiCl₄ gas and NH₃ gas is stopped, and the interiorof the chamber 1 is purged with N₂ gas.

Thereafter, in the state in which the wafer W after film formation isstill placed on the susceptor 2, the opening/closing valve 73 is openedto supply DCS gas, which is a Si-containing gas, into the chamber 1,which is a processing container. At this time, N₂ gas as a carrier gasis supplied from at least the third N₂ gas source 56.

By performing the Si-containing gas supply step which is apost-film-formation process in this way, DCS gas, which is aSi-containing gas, is adsorbed on the surface of the TiN film formed onthe wafer W, and as illustrated in FIG. 6 , a Si-containing layer isformed as a surface layer 304 on the surface of the TiN film 303 formedon the wafer W. The Si-containing layer constituting the surface layer304 may be a Si layer formed by heating a Si-containing gas or may alayer that includes, in Si, TiSiN formed by the reaction of Si and TiN.

As the conditions when supplying the DCS gas, the temperature of thesusceptor 2 is preferably set to 400 to 600 degrees C., and the pressurewithin the chamber 1 is preferably set to 266.6 to 13,332.2 Pa (2 to 100Torr). Conditions similar to this may be used for other Si-containinggases. The temperature of the susceptor is preferably the same as thetemperature when forming the TiN film, from the viewpoint of notlowering a throughput.

As described above, since the Si-containing gas forms the surface layer304 by being adsorbed on the surface of the TiN film 303 formed on thewafer W, the wafer W is carried out in a state in which the surface ofthe TiN film 303 is not exposed. Therefore, even if the wafer W isexposed to the atmosphere, the oxidation of the TiN film 303 issuppressed, and thus it is possible to prevent the resistance of the TiNfilm 303 from increasing. In particular, when the film thickness of theTiN film 303 is reduced to 5 nm or less, the influence of oxidationincreases. Thus, the oxidation suppression effect by the supply of DCSgas, which is a Si-containing gas, becomes higher.

The supply of Si-containing gas may be performed once or repeatedmultiple times. When the supply of the Si-containing gas is performedonce, it is possible to control the adsorption amount by the supplytime. In this case, the supply time of the Si-containing gas, such asDCS gas or SiH₄ gas, is preferably 1 to 20 sec. In addition, byrepeating the supply of Si-containing gas, DCS gas, SiH₄ gas, or thelike multiple times, it is possible to control the adsorption amount ofDCS gas, SiH₄ gas, or the like by the number of times of repetition, andthus it is possible to enhance the controllability of the thickness ofthe surface layer 304. Therefore, it is possible further lower theresistance of the TiN film. In this case, the supply time of DCS gas,SiH₄ gas, or the like at one time is preferably in the range of 0.05 to4 sec, and the number of times of supply (number of cycles) of DCS gas,SiH₄ gas, or the like is preferably in the range of 1 to 5 times. Thesame is also applicable to the case in which another Si-containing gasis used. When the supply of the Si-containing gas is repeated multipletimes, it is preferable to purge the interior of the chamber 1 with N₂gas between the cycles of supplying of the Si-containing gas.

The specific gas supply sequence of the TiN film forming step and theSi-containing gas supply step in this case is illustrated, for example,in FIGS. 7 and 8 . Here, the case in which DCS gas or SiH₄ gas is usedas the Si-containing gas is shown. FIG. 7 is a timing chart when DCS gasor SiH₄ gas as the Si-containing gas is supplied once (1 cycle), andFIG. 8 is a timing chart when DCS gas or SiH₄ gas is supplied multipletimes (multiple cycles).

NH₃ gas may be supplied during the Si-containing gas supply step, whichis the post-film formation process. In this case, NH₃ gas may besupplied after supplying the DCS gas or the SiH₄ gas as theSi-containing gas, or the DCS gas or the SiH₄ gas and the NH₃ gas may bealternately supplied multiple times. By supplying the DCS gas or theSiH₄ gas and the NH₃ gas, it is possible to form a SiN layer as thesurface layer 304. By supplying these gases alternately multiple times,it is possible to further enhance the uniformity of the film thickness.The specific gas supply sequence of the TiN film forming step and theSi-containing gas supply step in this case is, for example, illustratedin the timing chart of FIG. 9 . FIG. 9 illustrates an example in which,after the film forming step is completed, the supply of TiCl₄ gas isstopped, purging is performed, and then NH₃ gas and DCS gas or SiH₄ gasare alternately supplied multiple times.

After the step of supplying the Si-containing gas, the opening/closingvalve 73 is closed to stop the supply of DCS gas, which is aSi-containing gas, and the interior of the chamber 1 is purged with N₂gas. Next, the gate valve 27 is opened, and the wafer W is carried outthrough the carry-in/out port 26.

Regarding a case in which the Si-containing gas supply step was notactually performed after forming a TiN film having a thickness of 3 to 5nm through an ALD method, and a case in which the supply of DCS gas wasperformed as the Si-containing gas supply step under various conditions,changes in resistivity after being left in the atmosphere wereinvestigated. FIG. 10 is a diagram showing the relationship between theflow rate of DCS gas and the specific resistance of a TiN film, and FIG.11 is a diagram showing the relationship between the supply time of DCSgas and the specific resistance of a TiN film. The temperature of theDCS gas supply step was set to the range of 450 to 500 degrees C., thepressure was set to the range of 266.6 to 1,199.9 Pa (2 to 9 Torr), andFIG. 10 shows the case in which the supply time of DCS gas was 0.05 sec,and FIG. 11 shows the case in which the flow rate of DCS gas was 30sccm. As shown in these figures, by performing the Si-containing gassupply step, the specific resistance (μΩ·cm) after being left in theatmosphere was reduced. Thus, the effect of suppressing the surfaceoxidation of the TiN film by the DCS gas supply step was confirmed. Itwas confirmed that the specific resistance decreases as the flow rate ofDCS gas increases and the supply time of DCS gas increases.Specifically, it was confirmed that when the flow rate was set to 100sccm, the specific resistance was reduced by 26.8%, and when the timewas set to 10 sec, the specific resistance was reduced by 37.8%.

Next, regarding a case in which, as the Si-containing gas supply step,the supply of SiH₄ gas was performed once (1 cycle) and a case in whichthe supply of SiH₄ gas was performed 5 times (5 cycles) with purginginterposed between cycles, the sheet resistances (Ω/sq.) of TiN filmsafter being left in the atmosphere were measured. For comparison, thesheet resistances were also measured regarding a case in which thesupply of SiH₄ gas was not performed after the formation of the TiNfilm. Here, the supply time and flow rate of SiH₄ gas per one timesupply were set to 0.05 sec and 50 sccm, respectively, the temperaturein the Si-containing gas supply step was set to the range of 450 to 700degrees C., and the pressure was set to 266.6 to 1,199.9 Pa (2 to 9Torr). The sheet resistances of the TiN films and the uniformitiesthereof at that time are shown in FIG. 12 .

As shown in FIG. 12 , when the Si-containing gas supply step was notperformed, the average value of sheet resistances was 44.4 Ω/sq. and theuniformity was 3.9%, whereas, when the number of times (cycles) ofsupplying SiH₄ gas was one (1 cycle), the average value of sheetresistances was 39.1 Ω/sq. and the uniformity was 1.2%, and when thenumber of times (cycles) of supplying SiH₄ gas was five (5 cycles), theaverage value of sheet resistances was 38.9 Ω/sq. and the uniformity was1.0%. That is, the specific resistance and the uniformity thereof wereimproved by performing the supply of SiH₄ gas, and the specificresistance and the uniformity thereof were further improved by supplyingSiH₄ gas multiple times.

Next, regarding a case in which, as the Si-containing gas supply step,each of SiH₄ gas and NH₃ gas was supplied one time (1 cycle), and a casein which SiH₄ gas and NH₃ gas were alternately supplied 5 times (5cycles) with purging interposed between cycles, the sheet resistances(Ω/sq.) of TiN films after being left in the atmosphere were measured.Here, the supply time and flow rate of SiH₄ gas per one time were set to0.05 sec and 50 sccm, respectively, and the supply time and flow rate ofNH₃ gas per one time were set to 0.05 sec and 600 sccm, respectively.The temperature of the Si-containing gas supply step was set to therange of 450 to 700 degrees C., and the pressure was set to the range of266.6 to 1,199.9 Pa (2 to 9 Torr). The sheet resistances of the TiNfilms and the uniformities thereof at that time are shown in FIG. 13 .FIG. 13 also shows the results when the Si-containing gas supply step ofFIG. 12 was not performed.

As shown in FIG. 13 , the average value of sheet resistances when theSi-containing gas supply step was not performed was 44.4 Ω/sq. and theuniformity thereof was 3.9%, whereas, when the number of times ofsupplying SiH₄ gas and NH₃ gas was one, the average value of sheetresistances was 39.7 Ω/sq. and the uniformity thereof was 1.2%, and whenthe number of times of supplying SiH₄ gas and NH₃ gas was five, theaverage value of sheet resistances was 39.1 Ω/sq. and the uniformitythereof was 1.2%. That is, the sheet resistance and the uniformitythereof were improved by performing the supply of SiH₄ gas and NH₃ gas,and the sheet resistance was further improved by supplying SiH₄ gas andNH₃ gas multiple times.

After supplying the Si-containing gas to form the surface layer 304 ofthe TiN film 303, the wafer W is taken out into the atmosphere, andthen, as illustrated in FIG. 14 , a film forming process in the nextstep, for example, formation of a SiGe film 305, is performed in anotherfilm forming apparatus. Then, after the necessary post-processing isperformed, a desired semiconductor device is obtained. At this time,since the surface layer 304 containing Si is formed on the surface ofthe TiN film 303 by the supply of the Si-containing gas, the oxidationof the TiN film 303 is suppressed and the specific resistance ismaintained low. Therefore, a good device characteristic is obtained.

Since the film formed in the next step is the SiGe film 305, which is aSi-containing layer, the film has a high affinity with respect to theSi-containing surface layer 304 formed for suppressing oxidation. Inaddition, since the formation of the SiGe film in the next step isperformed on the surface layer 304 containing Si in this way, effectssuch as shortening of incubation time are obtained when the SiGe film isformed through a general CVD method.

<Other Applications>

Although embodiments have been described above, it should be consideredthat the embodiments disclosed herein are exemplary in all respect andare not restrictive. The embodiments described above may be omitted,replaced, or modified in various forms without departing from the scopeand spirit of the appended claims.

For example, the above-described embodiments have been described mainlywith reference to the case in which a TiN film is formed as ametal-based film through an ALD method, but as described above, thepresent disclosure is applicable to a metal film and a metal compoundfilm as long as the films have characteristics that may be deterioratedby oxidation. Furthermore, the film forming method is not limited to theALD method.

As the film forming apparatus of FIG. 3 , an apparatus for ALD filmformation of a TiN film has been exemplified, but the film formingapparatus of FIG. 3 may also be applicable to film formation of othermetal-based films. The film forming apparatus illustrated in FIG. 3 ismerely an example and may be any film forming apparatus, such as a CVDfilm forming apparatus or a PVD film forming apparatus, as long as afilm forming process and supply of a Si-containing gas into theprocessing container (chamber) can be performed. Although the filmforming apparatus of FIG. 3 is a single-wafer type, the film formingapparatus may be a batch type film forming apparatus that forms a filmon a plurality of substrates at once, such as a vertical type apparatus.In addition, the film forming apparatus may be a semi-batch type filmforming apparatus in which a plurality of substrates are placed on astage to perform a film forming process.

Furthermore, in the embodiments described above, a semiconductor waferhas been described as an example of a substrate, but the substrate isnot limited to the semiconductor wafer, and may be another substrate,such as a glass substrate used for a flat panel display (FPD) or aceramic substrate.

EXPLANATION OF REFERENCE NUMERALS

1: chamber, 2: susceptor, 3: shower head, 4: exhaust part, 5: gas supplymechanism, 6: controller, 51: TiCl₄ gas source, 52: NH₃ gas source, 53:DCS gas source, 54, 55, 56: N₂ gas supply source, 100: film formingapparatus, 201: substrate, 202: metal-based film, 203: surface layer,301: Si base body, 302; SiO₂ film, 303: TiN film, 304: surface layer, W:semiconductor wafer (substrate)

What is claimed is:
 1. A film forming method comprising: providing asubstrate into a processing container; forming a metal-based film on thesubstrate within the processing container; and subsequently, supplying aSi-containing gas into the processing container in a state in which thesubstrate is provided within the processing container.
 2. The filmforming method of claim 1, wherein by the supplying the Si-containinggas, the supplied Si-containing gas is adsorbed on a surface of themetal-based film, and a surface layer containing Si is formed on thesurface of the metal-based film.
 3. The film forming method of claim 1,wherein the substrate has temperature in a range of 400 to 600 degreesC. when performing the supplying the Si-containing gas.
 4. The filmforming method of claim 1, wherein the Si-containing gas is at least oneof a silane-based compound, a chlorosilane-based compound, and anorganic silane-based compound.
 5. The film forming method of claim 4,wherein the Si-containing gas is at least one of dichlorosilane, silane,and disilane.
 6. The film forming method of claim 1, wherein, in thesupplying the Si-containing gas, the Si-containing gas is suppliedmultiple times.
 7. The film forming method of claim 1, wherein, in thesupplying the Si-containing gas, the Si-containing gas and a reactiongas that reacts with the Si-containing gas are supplied.
 8. The filmforming method of claim 7, wherein, in the supplying the Si-containinggas, the Si-containing gas and the reaction gas are alternately suppliedmultiple times.
 9. The film forming method of claim 1, wherein theforming the metal-based film is performed through any of an ALD method,a CVD method, and a PVD method.
 10. The film forming method of claim 1,wherein the metal-based film is any of a Ti film, a TiN film, a Ta film,a TaN film, a W film, an Al film, a Mo film, a Ru film, a Co film, and aNi film.
 11. The film forming method of claim 1, wherein the metal-basedfilm is a TiN film, and the forming the metal-based film is performedthrough an ALD method.
 12. The film forming method of claim 11, wherein,by the supplying the Si-containing gas, the supplied Si-containing gasis adsorbed on a surface of the metal-based film, and a surface layercontaining Si is formed on the surface of the metal-based film, and thesurface layer contains TiSiN.
 13. The film forming method of claim 11,wherein the Si-containing gas is dichlorosilane.
 14. The film formingmethod of claim 11, wherein, in the supplying the Si-containing gas, theSi-containing gas is supplied multiple times.
 15. The film formingmethod of claim 11, wherein formation of the TiN film is performed usinga Ti-containing gas and NH₃ gas, and in the supplying the Si-containinggas, the Si-containing gas and the NH₃ gas are supplied.
 16. The filmforming method of claim 15, wherein, in the supplying the Si-containinggas, the Si-containing gas and the NH₃ gas are alternately suppliedmultiple times.
 17. The film forming method of claim 11, wherein thesubstrate includes a patterned SiO₂ film formed on a semiconductor basedbody.
 18. A film forming apparatus comprising: a processing containerconfigured to accommodate a substrate therein; a gas supply mechanismconfigured to supply a gas for forming a metal-based film and aSi-containing gas into the processing container; an exhaust mechanismconfigured to evacuate an interior of the processing container; aheating mechanism configured to heat the substrate; and a controller,wherein the controller is configured to perform control to execute:providing the substrate into the processing container; forming themetal-based film on the substrate within the processing container; andsubsequently, supplying the Si-containing gas into the processingcontainer.
 19. A method for manufacturing a semiconductor device, themethod comprising: providing a substrate into a processing container ofa first film forming apparatus; forming a metal-based film on thesubstrate within the processing container; subsequently, supplying aSi-containing gas into the processing container in a state in which thesubstrate is provided within the processing container; and carrying outthe substrate from the processing container and forming a Si-containingfilm on the substrate by a second film forming apparatus.
 20. The methodof claim 19, wherein, in the supplying the Si-containing gas, theSi-containing gas is supplied multiple times.
 21. The method of claim19, wherein, in the supplying the Si-containing gas, the Si-containinggas and a reaction gas that reacts with the Si-containing gas aresupplied.
 22. The method of claim 21, wherein, in the supplying theSi-containing gas, the Si-containing gas and the reaction gas arealternately supplied multiple times.
 23. The method of claim 19,wherein, in the supplying the Si-containing gas, the suppliedSi-containing gas is adsorbed on a surface of the metal-based film, asurface layer containing Si is formed on the surface of the metal-basedfilm, and the Si-containing film is formed on a surface of the surfacelayer.
 24. The method of claim 23, wherein the metal-based film is a TiNfilm, and the Si-containing film is a SiGe film.
 25. The method of claim24, wherein the substrate includes a patterned SiO₂ film formed on asemiconductor base body.